Canine Leishmaniosis is caused by a small parasite that lives inside cells. The disease is spread by infected sand flies which pass the parasite from one animal to another when they bite and feed. The disease occurs in warm climates, e.g. Central and South America, the Middle East and Mediterranean regions. In these areas as many as 4 out of 10 dogs are infected. Dogs travelling into or through these areas can be infected.
Sand flies often live in woodland areas but recently they have adapted to survive in areas close to human habitation especially in South America. Sand flies are more common during the warmer months of the year although, with climate change, the seasonal period for transmission is increasing. Most sand flies that spread leishmaniosis are most active (and will bite) between evening and dawn. They are small flies and may not be easily seen.
Most affected dogs have swollen glands (swellings in the armpits, groin, around the throat) although these may not be obvious in long-haired breeds. Dogs may have poor appetite, listlessness, unwillingness to exercise and weight loss.
Skin problems are often seen. These may include loss of hair especially around the head and ears, scaly skin, swellings and ulcers on legs, foot pads and other areas including the mouth and tongue. Ulcers and inflamed areas can appear around the lips, nose, eyes and, especially, the tips of the ears. The nails may become very long and brittle.
Other signs may be seen depending on the area of the body affected and include lameness, eye problems, bleeding from the nose, drinking or urinating too much, vomiting and/or diarrhoea.
Joints may also be damaged by the disease and this causes lameness, stiff gait and swollen limbs.
Signs of disease may develop a long time after infection (up to several years) or within a few months of being exposed to an infected sand fly. It all depends on how susceptible your dog is and the number of sand fly bites.
You should be concerned and consult your vet if your pet starts to show any of the signs of ill health mentioned above, after travelling abroad (or if it was born abroad). Always mention that your pet has spent time in a Leishmania area, whether they were adopted and then came in the UK, or if they have travelled to an area where leishmania occurs commonly – even if only for a few days.
As leishmaniosis is becomly increasingly common in the UK, more diagnostic techniques are being developed for vets. However, more than one test may be necessary to confirm if your dog has active infection or has just been exposed to an infected sand fly bite. Leishmaniosis can be confirmed with one or more of the following tests:
- Looking for the whole Leishmania organism or looking for the Leishmania DNA (PCR testing) in samples from blood, glands, smears from the eyelid, bone marrow or skin biopsies.
- Looking for very high antibody levels in blood.
In dogs that have been imported from endemic regions to countries where Leishmaniosis is not common, diagnosis may be delayed as the disease may not always be considered initially.
Treatment in dogs is much more difficult than in people and the disease in untreated dogs is commonly fatal. Even with current treatments it is still not possible to completely eliminate the parasite. However, treatment can often dramatically reduce the clinical signs of disease and improve a dog’s quality of life. However, continued treatment may be needed life long in an infected animal to keep the parasite under control.
Treatment is not straightforward. There are licensed drugs in continental Europe for the treatment of leishmaniosis but these are not yet available in the UK. Your vet will have to do two things to obtain the right drugs:
- Contact a drug company which will import the drug into the UK for your pet
- Obtain a special certificate from the UK Veterinary Medicines Directorate that shows that all details about the drug comply with UK standards
Treatment can be expensive and rarely results in a cure. Dogs that look very well can still harbour small numbers of parasites deep in some organs such as the bone marrow. Before treatment your vet will want to check your dog’s kidney function, liver function and immune system. The drugs used are very powerful and may produce significant side effects if the disease has already caused kidney or liver damage. If your dog has serious kidney problems. unfortunately the outlook is likely to be poor.
The most successful methods of treatment involve using a combination of different drugs. The most commonly used drugs are meglumine antimonate and allopurinol, but the combination of the new drug miltofisine with allopurinol may be a good alternative.
At present dogs that have never travelled outside the UK are at very low risk of developing leishmaniosis. However, if the sand fly manages to establish within the UK, this will change.
If you are taking your dog abroad to a country where leishmaniosis is common then it is important to protect them against biting sand flies. Dogs should be kept in during the evenings (when the flies are most active) and certain insecticides (synthetic pyrethroids) in spot-on and collar formulation with fly repellent activity should be used. None of these products provides 100% protection.
A vaccine for leishmaniosis in dogs has now been developed (CaniLeish® – registered by the European Medicines Agency in 2011).
Bites from infected sand flies are the major route of transmission of leishmaniosis. Just like dogs, people are usually infected by being bitten by sand flies. If you are visiting an area where leishmania is known to be common it is vital that you apply repellant insecticides on yourself (as well as your dog).
There are no published reports of direct infection from an infected dog to a human without a sand fly vector being involved. However, there are reports of transmission of infection from human to human by blood transfusions and contaminated needles. There are also rare reports of transmission from dog to dog without the sand fly vector. Considering this, general advice would be to limit contact between infected dogs and children or adults with a poorly functioning immune system.